1. Fields of the Invention
The present invention relates to a radiotracer precursor, especially to a radiotracer precursor containing an organic ligand, 6-(2-nitroimidazole)hexyl-DL-2,3-Bis-[((triphenylmethyl)thio)acetamido]propanamide (BANI), a radiotracer and a method for preparing the same.
2. Descriptions of Related Art
A plurality of diseases may cause hypoxia and further brings tissues or organs have insufficient oxygen supply. For example, tissues of patients with serious diseases such as stoke, myocardial infarction, malignant tumor, etc. have decreased oxygen supply, hypoxia. The hypoxia is resulted from acute or temporarily reduction of regional blood flow at myocardial cells or insufficient oxygen supply to malignant cells and is unpredictable. Thus a lot of non-invasive techniques for detecting hypoxia at various regions such as heart, brain, tumor have been developed vigorously.
All mammals require oxygen for tissue metabolism. Generally metabolism/reaction in cells only needs low concentration oxygen (about 3˜5 torr) flowing from capillaries to cells nearby. But malignant cells change oxygen balance in tissues. Tumor cells need additional oxygen supply to maintain cell activity. In order to meet such requirement, tumor cells induce blood vessel growth in tissues. However, the amount of oxygen the tumor cells require is always much larger than the amount of oxygen the blood vessels supply. Once oxygen diffuses across the wall of capillaries, it is quickly metabolized by cells on outer layers and unable to diffuse into inner layers of tumor cells. Thus cells inside large solid tumors are in hypoxia due to insufficient oxygen and blood supply and necrosis occurs gradually during long term hypoxia. There is a certain ratio of hypoxic or necrosis cells in tumors and the ratio is related to volume and biological characters of tumors.
Therefore hypoxic tissues are of great potential, as media/targets being detected by radionuclide imaging techniques for diagnosis and follow-up of the malignant tumors.
Nuclear medicine imaging involves applications of radioisotopes in medical imaging for patients. Radiopharmaceuticals are delivered into patients' bodies by intravenous injection, oral intake, inhalation etc. After a period of time, the radiopharmaceuticals are attracted to specific organs or tissues. Then medical imaging machines such as gamma cameras are used to detect distribution of the radiopharmaceuticals in organs or tissues. For example, crystal of sodium iodide in the camera scintillates in response to incident gamma radiation so as to form images. After development or computer processing, the images are used by doctors to detect physiological changes.
The drugs available now such as PnAO-NI and HL91 all contain diamine-dioxime ligands that bind to radioisotopes such as 99mTc etc. and apply to radiotracers for imaging hypoxic tissues. Yet 99mTc-PnAO-NI has high lipid solubility and 99mTc-HL91 has low high lipid solubility. Thus both are not suitable to be used in clinical imaging
A suitable radiotracer plays an important role in detection of tumor hypoxia in vivo by radionuclide imaging techniques.